APOCHROMAT LENS Russian patent published in 2017 - IPC G02B9/64 

FIELD: physics.

SUBSTANCE: objective lens consists of ten single lenses where the first and the last lenses are negative meniscus lenses with their convex sides facing an object, second lens is convex-convex, third, sixth and eighth ones are negative lenses with first concave surface, fourth, fifth and ninth lenses are positive lenses with first convex surface. The following ratio is observed for the fourth positive and the last negative lens: β₄=β₁₀<75⋅10^-7 1/K, while the other lenses match the following ratio: |β|<35⋅10^-7 1/K, where β₄, β₁₀, β are temperature factors of material refraction index of the fourth, last and the other lenses, respectively, K is Kelvin degree.

EFFECT: ensured heat stability of objective lens, expanded operation spectre range, field of view and focus distance without deterioration of image quality.

2 dwg, 1 tbl